Dental articulator

ABSTRACT

A dental articulator that simulates jaw movements in the same directions as the natural jaw. A lower jaw element is suspended from a fixed base by two pivots movable relative to the frame along restricted paths. An upper jaw element is pivotally supported by the base about a fixed axis coincident with one position of the movable pivots. Each jaw element forms a support for a dental arch cast. Each pivot can be individually locked in a fixed location and the lower jaw element can be released from the pivots for limited relative translational and rotational movement and adjusted to a new relationship with the pivots. Adjustable cam surfaces on the frame control lateral movement of the lower jaw element. A rigid link pivotally and releasably connected between the frame and lower jaw element restrains movement and establishes a chewing-type pivoted action. A plate on the lower jaw element is movable rectilinearly so that the anterior-posterior closed position of the teeth can be adjusted without changing the pivot axis. Plates with peripheral spongelike wall portions forming enclosures for plaster are adapted to be secured to the supporting jaw elements. The wall of each plate serves to support a dental arch cast and acts both as a plaster dam and as a compressive spring when opposed plates and dental arch casts are pressed in opposition on a bite registration to secure the cast to the articulator. An adjustable stop is secured to one support element for contact with the other support element to limit proximity of the jaw elements and is removable without changing its effective length.

United States Patent Derda et al.

[451 Sept. 30, 1975 154] DENTAL ARTICULATOR {76} Inventors: Harry J.Derda, 81 Powers Rd..

Bedford, Ohio 44146; Charles H. Gibbs. 1918 Southwest 48th Ave.,Gainesville, Fla. 32608 1221 Filed: June 20. 1973 [21] Appl. No.:371,702

[52] US. Cl. 32/32 [51] Int. Cl. A61C ll/00 [58] Field of Search 32/12.22, 32

[56] References Cited UNITED STATES PATENTS 2.097.701 11/1937 Pfeiffer32/32 2.204.809 6/1940 Miller et a1. 32/32 2.428.808 10/1947 Miller32/32 2.608.761 9/1952 Scott 32/32 2.748.481 6/1956 Glueck 32/323.343.264 9/1967 Guichet 32/32 3.359.639 12/1967 Guichet 32/32 3.387.3696/1968 Swanson 32/32 3.409.986 11/1968 Freeman 3 /32 3.590.487 7/1971Guichet 3.772.788 11/1973 Gerber Primary Examiner-Robert PeshockAttorney. Agent, or FirmWatts. Hoffmann. Fisher & Heinke Co.

[57] ABSTRACT A dental articulator that simulates jaw movements in thesame directions as the natural jaw. A lower jaw element is suspendedfrom a fixed base by two pivots movable relative to the frame alongrestricted paths. An upper jaw element is pivotally supported by thebase about a fixed axis coincident with one position of the movablepivots. Each jaw element forms a support for a dental arch cast. Eachpivot can be individually locked in a fixed location and the lower jawelement can be released from the pivots for limited relativetranslational and rotational movement and adjusted to a new relationshipwith the pivots. Adjustable cam surfaces on the frame control lateralmovement of the lower jaw element. A rigid link pivotally and releasablyconnected between the frame and lower jaw element restrains movement andestablishes a chewingtype pivoted action. A plate on the lower jawelement is movable rectilinearly so that the anterior-posterior closedposition of the teeth can be adjusted without changing the pivot axis.Plates with peripheral spongelike wall portions forming enclosures forplaster are adapted to be secured to the supporting jaw elements. Thewall of each plate serves to support a dental arch cast and acts both asa plaster dam and as a compressive spring when opposed plates and dentalarch casts are pressed in opposition on a bite registration to securethe east to the articulator. An adjustable stop is secured to onesupport element for contact with the other support element to limitproximity of the jaw elements and is removable without changing itseffective length.

52 Claims, 14 Drawing Figures U.S. Patent Sept. 30,1975 Sheet 2 of63,908,271

US. Patent Sept. 30,1975 Sheet 3 of 6 3,908,271

US. Patent Sept. 30,1975 Sheet 5 of6 US. Patent Sept. 30,1975 Sheet 60f6 3,908,271

DENTAL ARTICULATOR BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to dental articulators.

2. Prior art The general purpose of an articulator mechanism is to movecast replicas of dental arches relative to one another through theintercuspal range and to their closed position. The movements and closedpositions attainable on an articulator are important in attaining afunctional restoration of teeth. An articulator, along with a compatibleface bow system, aids a dentist in diagnosing the articulation andocclusion of a particular patient and aids him in constructingrestorations outside of the mouth.

Good articulation and occlusion are important for oral health, comfortand aesthetics, and in the case of denture wearers, are important tomaintain the periodontal structures, denture stability, chewingefficiency, and comfort. In cases of improper tooth arrangement andcontour, forces can be generated during articulation and occlusion thattraumatize the toothsupporting structures, thereby weakening toothsupport, increasing tooth mobility and increasing the likelihood ofperiodontal infection. In some instances improper tooth-to-tooth contactcauses forces at the temporomandibular joints that result in a musclespasm pain syndrome.

The process of dental restoration is long and involved. An articulator,when used with a face bow, in effect puts the patients head on theworkbench where lengthy construction procedures can be made withoutdiscomfort or hazard to the patient. Moreover, functional jaw movementsrequired to design and evaluate restorations are difficult to generateconsciously in the mouth. In practice, mechanically reproduciblemovements based on preconscious functional recordings of jaw movementsare preferable.

The articulator is typically used with a face bow measuring system thatrelates the particular patients temporomandibular joints to his dentalarches, and a bite registration to relate the dental arches, one to theother, so that the dental arches can be properly positioned on thearticulator.

The face bow insures the accuracy of the bite registration by indicatingwith pointers that the jaw is in the desired position while theimpressionable material on the bite registration records the imprints ofthe cusp tips. Among other functions it also serves to approximatelylocate the particular patients temporomandibularjoints with respect tohis dental arches. The bite registration is preferably thin andtypically includes an impressionable material. When affixed to the facebow and clamped between the teeth of the patient, it records arelationship between the teeth and the temporomandibular joint, that canbe transferred to the articulator.

The complex movements of the jaw have been recognized for some time.See, for example, the article published in 1908 by NC. Bennett entitledA Contribution to the Study of the Movement of the Mandible [Proceedingsof the Royal Society of Medicine (Odont. Sect.) Vol. I (3)]. A greatmany articulators have been designed for dental use. According to athesis by James E. House (The Design and Use of Dental Articulators inthe United States from 1840 to 1970 Masters Thesis, School of Dentistry,Indiana University, 1970) 235 dental articulators were patented in theUnited States during the period 1840 to 1970. Typically, earlyarticulators were of the so-called hinge type in which twosuperpose'd'support plates were used, one fixed and one supported forsimple pivotal movement toward and away from the other. Also, see US.Pat. No. 1,574 issued Apr. 30, 1940 and purportedly the first patent tobe issued on an articulator. More sophisticated articulators hinge theupper plate for translational and rotational movement, sometimes throughthe use of adjustable shafts, to simulate the temporomandibular joint.Movement of the hinged plate is controlled by the joint construction,which may include condylar elements in condylar guide housings.Typically, a pin would be provided on the pivoted jaw member and anincisal guidance table provided on the fixed frame to guide the movablejaw in chewing movement. In contrast, an articulator using only a hingemovement lacks chewing closure movement.

Articulation with pivoted upper plates have resulted in a reversal ofmovements from that of the normal jaw. Also, attempts to provide thevariety of necessary movements and adjustments to accommodatedifferences in measurements for patients has resulted in complexarrangements that have practical limitations and are difficult to use.Yet, for the modern practitioner, the dental articulator must providemany different jaw positions and perform many movements throughdifferent mechanisms. The ease and simplicity with which an articulatorcan be adjusted to provide the needed positions and perform the neededmovements accurately and precisely, largely determine its usefulness.

SUMMARY OF THE INVENTION The present invention provides a dentalarticulator that incorporates the necessary adjustments and movements toproduce the necessary flexibility and motions to attain the neededpositions and movements for diagnosing articulation and occlusion and toaid in constructing restorations. At the same time, the articulatorembodying the present invention is of simplified construction readilyadjustable without the need for tools, and will perform the differentmovements required accurately and precisely. It has the particularadvantage of simulating the natural movements of a lower jaw in thenormal relationship to the upper jaw by utilizing a jaw elementconnected to a frame in an orientation analogous to the natural positionof the jaw in the skull.

Most desirably, an articulator must be capable of closely duplicatingjaw chewing movement; i.e., the socalled working condyle of thearticulator, corresponding to the condyle on the pressure applying sideof an actual jaw, should move medially or sideways while the non-workingcondyle moves along a constraining path analogous to thetemporo-mandibular fossa and controls the extent of the medial movementof the working condyle. The movement of the front, i.e., tooth area, ofthe movable articulator jaw must also,be suitably constrained along adesired approach angle to the fixed jaw. The articulator embodying thepresent invention attains this capability through a minimum ofadjustments and constraints to assure the necessary flexibility andmovements without undue mechanical complexity. An instantaneous screwaxis analysis of actual jaw movement and of the present articulatormovement shows that the movable articulator jaw moves throughessentially the same instant axes as an aactual jaw, during typicalchewing movement.

Basically, the present invention is comprised of two relatively movablejaw elements for supporting dental arch casts, and specific adjustmentsand constraints for the jaw elements. A lower jaw element is adjustablysupported, e.g. by a support frame, for complex translational androtational movement, to simulate chewing jaw movement and to facilitatetooth gliding. The upper jaw element is supported, as by the same frame,for simple pivoting about a single axis to provide access to the dentalarch casts and for establishing maximum intercuspal position, i.e.,closed position. The device is constructed to locate dental arch castssupported by the jaw elements in a forward location relative to thesupporting portions of the apparatus frame, accessible for work and viewwithout interference from the frame, pivot structure or constraintsassociated with the pivoted jaw member.

Movement of the lower jaw element is controlled by two joint constraintsabove a dental arch cast support portion and a prime link constraintbetween the jaw element and frame. The link constrains one degree offreedom of the jaw element movement, helps define the approach of thelowerjaw element relative to the upper element, and in additionestablishes functional chewing movement. The link is adjustable in itseffective length and angle between the support frame and jaw element tovary the angle and range of movement of the jaw element. It is alsoreleasable to permit hinge type pivoting and tooth gliding movement ofthe lower element, or the use of an incisal table for controlling jawelement movement. Pivot mechanisms include a number of adjustments forreleasing the repositioning the lower jaw element and for permittingsideward movement and guided sliding movement, analogous to that of thecondyles of the jaw on the fossae of the skull. The pivot mechanisms areadjustable for different dimensions that may be required when working ondental casts for different individuals. The adjustments are useful toindicate the difference between a position determined from a biteregistration mounting and the existing (ac' quired) closed position asdetermined by the teeth and further permit the quick remounting ofdental casts to any bite registration or the comparison of a number ofbite registrations with the cementing position of the dental arch caststo thereby compare the bite registrations one with another. In thismanner, the device serves the same function as the known split-casttechnique, but provides greater speed and indicates the amount of anydiscrepancy. The adjustments include, in particular, the independentsetting of the slope of the structures analogous to the fossae and thesetting of a desired intercondylar distance. A side shift of the pivotsis provided to increase the effective lateral movement which is usefulfor developing clearances of posterior teeth and lateral movements aswell as to develop a sideward freedom of movement at the closedposition.

Each pivot mechanism provides a first lock for adjustably positioningthe angle of the condyle-guiding structure analogous to the fossa slope,and a second lock for separately and selectively restraining orreleasing each condyle pivot of the lower jaw to prevent or allowmovement of either or both along the guiding fossae slopes. When bothcondyle pivots are restrained by the second lock, the lower jaw pivotsabout a single fixed axis. As a further feature of the pivot mechanisms,each condyle pivot can be released relative to the lowerjaw and the jawfreely moved and/or adjusted with respect to the condyle elements in twodegrees of 5 freedom.

Adjustable spring tension mechanisms are provided for the lower jawmechanism to adjust the closing force of the lowerjaw to the desiredfeel, or to completely release spring tension as when the condyle pivotsof the jaw are released relative to the jaw in determining the existingor acquired closed position applicable to the supported dental archcasts.

A mechanism comprising a rectilinearly adjustable slide surface iscarried by the lower jaw to accurately correct for overretrusion of thejaw by bringing the jaw straightforward from a retruded position ratherthan down the fossae slopes, and to develop anteriorposterior clearancebetween the dental arch casts.

The upper jaw hinge movement is selectively controlled by a lockmechanism that is positive in action and cam controlled, to selectivelypermit pivoting movement. The upper jaw mechanism carries an anteriorstop and incisal pin constructed so that the pin can be removed withoutchanging its setting. The pin controls the distance between the upperand lower jaw elements and can be adjusted to open the bite tocompensate for thickness of articulating papers and to change thefreeway space. It can also be used as a cam follower on an incisal tableand can be used to make jaw movement tracings.

A novel mounting plate is provided for use with each jaw element tofacilitate support of the dental arch casts. Each mounting plateincludes a rigid back member and a peripheral sponge-like wall portionforming a peripheral surface against which the back surface of thedental arch cast rests and further forming an enclosure for plaster. Byvirtue of the sponge-like construction of the peripheral wall, a nearlyconstant and uniform holding pressure can be exerted against opposedcasts, to maintain the casts in a desired relationship as plaster ispoured between the casts and supporting plate, and within the peripheralwall. With this arrangement, both casts can be mounted concurrently andthe plaster is to t the area desired. The construction of the supportframe facilitates orienting the jaw elements vertically so that plastercan be easily supplied to the zones defined by the peripheral spongewalls.

It will be apparent from the above that a general object of thisinvention is to provide an improved dental articulator that supportsdental arch casts in a natural relationship and in a position relativeto the frame that facilitates working and viewing without obstruction,that mechanically reproduces jaw movement and jaw position as they occurfunctionally in the mouth, and that can be conveniently and easilyadjusted to relate the dental arch casts to a particular patientstemporomandibular joints. More specific objects as well as otherfeatures and advantages of the invention will become apparent from thedetailed description that follows, when considered in connection withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofan articulator embodying the present invention;

FIG. 2 is a top plan view of the articulator of FIG. 1;

FIG. 3 is a front elevational view of the articulator of FIG. 1;

FIG. 4 is a partial sectional view taken along the line 4-4 of FIG. 1;

FIG. 5 is a partial sectional view taken along the line 5-5 of FIG. 1;

FIG. 6 is a partial sectional view taken along the line 6-6 of FIG. 1;

FIG. 7 is a partial sectional view taken along the line 77 of FIG. 1;

FIG. 8 is a partial sectional view taken along the line 8-8 of FIG. 1;

FIG. 9 is an exploded perspective view of the shaft and one condylepivot assembly of FIG. 4;

FIG. 9A is a perspective view of a modified embodiment of one part ofthe condylepivot assembly of FIG.

FIG. 10 is a partial side elevational view of the apparatus of FIG. 1oriented with the jaw elements vertical to facilitate cementing of thedental arch casts to the articulator;

FIG. 11 is a perspective view, with parts broken away and parts insection, of the incisal pin that forms a part of the articulator;

FIG. 12 is an elevational view with parts in section of a link pin thatforms a part of the articulator; and

FIG. 13 is an exploded perspective view of a mounting plate and spongewall used to support a dental arch cast in accordance with a preferredembodiment.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT A dental articulatorembodying the present invention is indicated generally by referencenumber in the drawings, and basically comprises a stand 22, a maxi]-lary or upper jaw member 24, and a mandibular or lower jaw member 26,which members are constructed to hold upper and lower dental arch castsDU and DL in a natural, opposed relationship, as illustrated in phantomin FIG. 1. The stand is constructed to orient the jaw members in twodirections, one in which they extend substantially horizontally as shownin FIG. 1, and a second position in which the stand is placed on itsback, with the jaw members in a substantially vertical direction asshown in FIG. 10, especially useful for initially mounting the dentalarches. Both jaw members 24, 26 are pivoted to the stand 22 tofacilitate access to the dental arches and to permit articulation of thelower jaw, for chewing and gliding movements, relative to the upper jawmember.

The stand 22 is constructed to support the articulator on a flathorizontal surface, and for that purpose is provided with a U-shapedbase 28, from which an L- shaped upright member extends, one leg 30a ofwhich extends vertically from the back of the base and another leg 30bof which extends forwardly over the base to support the jaw members 24,26 in cantilever fashion. In the embodiment shown, the leg 30b isreceived in a slot of the base 28 and is secured by a screw 32. Athrough bore 34 (FIG. 4) is formed in the distal end portion of the leg30b to receive a cylindrical shank 36 that extends transversely of theleg 30a and parallel to the plane of the U-shaped base 28. Two jointarea socket-like pivot structures indicated generally at 38 and 39 arecarried by the shaft 36, one at each end, and cooperate with ball-likepivot structures of the lower jaw element to articulate the lower jawelement relative to the stand in a manner generally analogous to themanner in which the fossae and condyles of the temporomandibular jointpivot the human jaw.

The upperjaw member 24 is comprised of a plate 42 with a hinge structure43 at the back end, that receives the end of the leg 30b that journalsthe shaft 36. A transverse surface 44 of the hinge structure 43 (seeFIG. 3) abuts the lower surface of the leg 30b, to pre vent the plate 42from pivoting toward the lower jaw element beyond a horizontal positionparallel to the base of the stand. Upward pivoting of the plate 42 to aposition slightly beyond or behind a vertical position is permitted bythe hinge structure. When the plate 42 is in a horizontal position, asshown in FIG. 1, a latch 46 pivotally carried by pin 48 on the leg 30bcan be engaged through a lever 49 with a notch 47 of the hinge structure43 to retain the plate in a lowered or horizontal position. Acompression spring 51 biases the latching lever 46 toward a non-latchingposition. A central aperture 54 is provided in ,the plate for receivinga screw 56 having a knurled knob 57 above the plate, for attaching adental arch cast. Depending locating pins 58, 59, are located ondiametrically opposite sides from the aperture 54, to locate and preventrotational movement of a dental arch cast. A front slot 60 (FIG. 2) isprovided in the plate 42, perpendicular to the hinge access, forreceiving an incisal guide pin 62.

The lower jaw element 26 is comprised of two parallel support arms 64,66 (see FIGS. 1 and 3) that pivota bly depend from the pivot structures38, 39 through condyle pivot assemblies 68, 69, at upper ends of thesupport arms, which are in part received in the pivot structures 38, 39.A crosspiece 70 connects lower ends of the two arms 64, 66, through atongue and groove junction that provides for adjustment of the distancebetween the two arms 64, 66. The position of each arm is secured by aknurled nut 72, 73, on a threaded post 74, 75, that extends from eacharm through a longitudinal slot in the cross piece 70. Calibrations 76are provided for each arm to facilitate centering or otherwisepositioning the cross piece and indicate the distance between the arms.

A mandibular plate 78 extends forwardly from the cross piece 70,supported on a tongue 80 that is partially recessed into a lower groove81 of the plate. The plate is secured to the tongue by a screw 82 thatis threaded in an aperture of the plate and that extends through a slot83 of the tongue. A spring washer 84 beneath the tongue yieldably biasesthe plate to the tongue for relative sliding movement. The plate is alsosecured to the tongue by an adjustment screw 85 rotatably secured to theplate 78 at a fixed location by a yoke 86. A fixed projection 87receives the screw 85 in a threaded bore, so that rotation of the screwslides the plate 78 rectilinearly toward and away from the cross piece70, relative to the tongue 80. Locating pins, 88, 89 and a knob 91similar to the knob 57 locate and secure a dental arch cast to the plate78.

For purposes of providing a restraint to motion of the lower jaw element26, a curved finger 90 extends rearwardly from the cross piece 70, in anopposite direction from the tongue 80, and downwardly toward the base ofthe stand. The finger has a central elongated slot 92. In the preferredconstruction, the curvature of the finger is of approximately but notexactly a uniform radius.

A restraining linkage 94 connects the lower jaw member 26 through thefinger 90 to the stand 22 to limit the freedom of movement of the lowerjaw element relative to the upperjaw element in a manner that willproduce a range of final closing movements of the jaw element as occurduring chewing, and which is constructed to be easily released tofacilitate tooth gliding and to adjust for the thickness of a biteregistration. The linkage provides a degree of restraint to movement ofthe lower jaw member 26 by fixing the distance of a point on the jawfrom a point on the stand. This linkage holds jaw movement to a desiredpath and, unlike an incisal pin and table, there can be no movementbeyond that permitted by the link, whereas an incisal pin can beinadvertently lifted from the guide table.

The linkage 94 is comprised of a universal joint 96 movable along theslot 92 to change the angle at which the link extends relative to aplane passing through the point of connection of the link to the standand the pivots of the lower jaw member, a universal joint 98 fixed tothe stand and located generally centrally of the curvature of the finger90, and a rigid link 100 connected to the universal joints in a mannerto facilitate adjustment of the effective length of the link.Alternatively to facilitating length adjustment, the location of one ofthe joints 96 or 98 could be movable to facilitate a change in angle andthe length of the link maintained constant.

As best shown in FIGS. 1, 3, 7 and 12 the link 100 is in the form of apin with an integral ball 103 at one end that forms a part of theuniversal joint 96. The ball 103 is received in a ball housing 104 thatrides in guided relationship within the slot 92 of the finger 90. A knob106 is threadedly secured to the ball housing 104 and serves to clampthe ball housing in a fixed position along the slot 92 when the knob istightened against the finger 90. In addition, the knob retains acompression spring 108 that spring loads a plastic bearing against theball 103 in a direction that biases the pin outwardly of the housing.

A slotted housing 110 rotatable about a horizontal axis transverse tothe link 100 supports a ball 1 12 of the universal joint 98. The housing110 is slotted at 114, so that the ball 1 12 lies in the path of theslot. The ball 1 12 has two cylindrical apertures along radii at rightangles, one of the apertures extending diametrically through the balland receiving the link 100, and the other aperture extending at rightangles thereto, communicating therewith and threaded to receive a setscrew 120. The ball 112 is spring-biased against the housing 110 by acompression spring 121 and slidable bearing block 122 within a supportbracket 123 in which the slotted housing is rotatable. A screw 124retains the spring under compression against the ball.

The pivot structures 38, 39 and condyle pivot assemblies 68, 69 togetherserve to connect the ends of the parallel jaw supports 64, 66 to thestand 22 for movement with three degrees of freedom, and are constructedto (a) serve as condyle range finders to indicate the difference inmounting position at the condylar element and along the condylar axes,between the acquired and ideal positions of the jaw, (b) act as pivotsthat allow restrained jaw movement simulating chewing motions of theteeth, and (c) permit release and reattachment of the jaw element toball pivots that act as condylar elements to adjust to a biteregistration or to otherwise change the relationship between dental archcasts secured to the mandibular and maxillary plates without recementingthe casts. Each of the pivot structures 38, 39 and condylar pivotassemblies 68, 69 is a mirror image of the other and therefore only thepivot structure 38 and associated condylar pivot assembly 68 will bedescribed in detail.

A ball element 130 of the assembly 68 is carried by the upper end of thejaw arm 64 and is received in a guide slot 132 formed in a cylindricalrotatable insert 133 of the pivot structure 38. The insert 133 iscarried in a cylindrical cup 134 secured to an end of the shaft 36 by ahub 135 received in a bore 137 of the shaft. The cup 134 is held inplace by a screw 138 that passes through an axially elongated slot 139in the wall of the bore 137 and threadedly received in the hub 135. Theguide slot 132 is the width of a ball 130a of the ball element 130. Anend surface 132a of the guide slot locates the ball with its centeraligned with the center of the pivot shaft 36. A back surface 132b ofthe slot is inclined at about 7 from a plane perpendicular to the axisof the shaft 36, as best seen in FIG. 6, inclining inwardly from the endsurface 132a toward the peripheral edge of the insert 133, through whichthe guide slot opens. This angle was established to produce a desiredsideways movement. Rotation of the insert 133 relative to thecylindrical cup 134 changes the angle of side surfaces l32c, 132d of theguide slot with respect to the axis of the shaft 36, so that the sidesurfaces can be adjusted to correspond to the slope of the fossa of thetemporomandibular joint, the function of which it simulates.

Adjustment of the rotatable insert 133 by rotation within thecylindrical cup 134 is made possible by a clearance fit between the two.An angular position is maintained through a clamping nut 141 on theoutside of the cup 134, threaded in clamping relationship therewith upona shaft 142 secured in the insert 133 and extending radially therefromthrough a peripheral slot 144 that extends partially around thecylindrical cup.

The ball 130a can be locked in a back position, against the end surface132a of the guide slot with a pin stop 146 (FIG. 5), controlled by ascrew 147 threaded through the shaft 142. The pin stop 146 is carriedwithin the rotatable insert 133 on the end of a cantilever spring 148secured at one end within a cavity of the insert. The pin stop 146 iscarried within the rotatable insert 133 on the end ofa cantilever spring148 secured at one end within a cavity of the insert. The pin stop ismovable on the spring lever into and out of the guide slot 132, and isbiased by the spring lever to a position out of the guide slot. An innerend of the screw 147 contacts the spring lever between the point ofattachment and the pin stop carried on the free end. By turning thescrew 147 to advance the screw inwardly, the pin stop 146 is moved intoengagement with the ball 130a. The location of the pin stop relative tothe end surface 132a of the rotatable insert is such that it will retainthe ball in the rearward position, while allowing the ball to rotate orpivot about its center. That is, the pin is spaced from the end surface132a down the slot 132 a distance equal to about three-fourths thediameter of the ball.

Lateral adjustment of the pivot structures 38, 39 so as to shift theposition of the guide slots and cooperating ball elements relative tothe upper jaw element, for purposes of a side shift to establish lateralfreedom of jaw movement, is facilitated by axial movement of the shaft36 relative to the L-shaped upright stand member 30. The axial positionof the shaft 36 is retained in or shifted to a desired position with twoadjustment screw knobs 150, 151, that are threaded in the enlarged endof the leg 30b and which abut a respective inclined surface 154, 155 ofthe shaft. The screws 150, 151 are inclined toward one another and actsubstantially perpendicularly to the inclined surfaces 154, 155. Thus,the two screws, cooperating with the respective inclined surfaces,locate the shaft 36 in a fixed axially position when the two screws arein direct contact with the respective surfaces. Upon retraction of onescrew and extension of the other, the shaft 36 can be shifted axially inone direction or the other. Separate lateral adjustment of each pivotstructure 38, 39 is facilitated by the associated screw 138 and theelongated slot 139. Any separate adjustment outward requires adjustmentof the distance between the support arms 64, 66 of the lower jawelement. Relative inward movement affords free sideways movement.

The ball element 130, in addition to having a ball 130a has a shaft 130bextending outwardly from the ball, with threads 1300 on the outer end.In addition, an integral flange 130d is carried by the shaft, spacedoutwardly from the ball a distance sufficient to permit the ball topivot within the guide slot 132. The flange 130d serves as a clampingsurface for the upper end of the support arm 64. A clamping nut 158 isreceived on the threads 130c and has a counter bore 159 that faces theflange 130d. Two diametrically opposite axial slots 161, 162 are formedat the end of the clamping nut, in the wall of the counter bore. Anannular centering guide 164 is slidable within the counter bore 159 andon the shaft l30b. Two diametrically opposite pins 165, 166 extend fromthe centering guide and are receivable within the slots 161, 162. Thelength of the pins extends beyond the periphery of the clamping nut andare receivedin apertures 167 of a knurled sleeve 168 that slidablysurrounds the clamping nut 158. The outside diameter of the centeringguide 164 is closely receivable within a circular aperture 170 in theupper end of the arm 64. The depth of the counter bore 159 issubstantially equal to the axial length of the centering guide 164, sothat the guide can be completely retracted into the counter bore. Thelength of the slots 161, 162 facilitate this movement. As a result ofthis construction, the centering guide can either be extended beyond theend of the clamping nut 158 so as to project into the aperture 170,thereby centering the shaft 130 relative to the aperture 170, or thecentering guide can be retracted into the counter bore 159 so that thelocation of the shaft 130 within the aperture 170 can be adjusted or sothe upper end of the arm 64 can float through an adjustable connectingrelative to the shaft 130, within the limits of the aperture 170. Ineither event, i.e., whether the centering guide is retractedor extended,the nut 158 is rotatable through the sleeve 168 and the pins 165, 166,to clamp the upper end of the arm 64 against the flange 130d. Rotationof the shaft 130 is restrained by a pin 172 that extends into a slot 173in the arm 64, directly beneath the circular aperture 170 to keep theelement 130 from rotating when the nut 158 is adjusted. The arrangementbetween the pivot assembly 68 and the arm 64 permits complete freedom ofmovement of the lower jaw element within a limited but adequate range sothat the relationship of the lower jaw element plate can be changedrelative to the pivot axis of the jaw element. The position of the lowerjaw element can therefore be set to work toward an existing closedposition; can be set with the centering element to work toward a closedposition as determined by the mounting bite registration; or can belocated in any desired relationship to the upper jaw element and lockedin the relationship for pivoting and translation as controlled by thepivot structure and restraining linkage. It will be appreciated thatreadjustment of the ball elements relative to the arms 64, 66 permitstilting of the lower jaw member about an axis perpendicular to the axisthrough the ball elements, i.e., in a manner to tilt the mandibularplate 78 and crosspiece so the left side, for example, is higher thanthe right side when viewed as in FIG. 3. When this adjustment is made,the shaft portions 13012 of the ball elements are no longer aligned (theball element shaft of assembly 69 is tilted upward from the ball and theother is tilted downward) but the centers of the ball elementsthemselves will remain aligned with the axis of the shaft 36 as long asthey are retained in a rearward position by the pin stops 146. When thestop pin is retracted, the ball is movable along the fossae slope, withthe lower jaw element having a new relationship with the upper element.

A modified clamping nut 158a is shown in FIG. 9A having a threaded bore171 for receiving threads 1300. A flat face 172 perpendicular to theaxis of the bore 171 clamps against the support arm 64 when the nut isoriented as shown, to hold the arm in an adjusted position. When the nutis reversed on the shaft b, a smaller diameter portion 173 is closelyreceived in the aperture of the arm 64 and centers the shaft 130relative to the aperture 170.

The lower jaw member 26 is yieldably biased toward the upper jaw memberby tension springs 174, 176. Each spring is attached at its lower end toa screw adjacent the base of each support arm 64, 66, one screw beingshown at 178 in FIG. 1. The upper end of each spring is secured to atension wheel 180, 182 rotatably supported on the shaft 36, directlyadjacent the pivot structures 38, 39, respectively. The tension wheel isshown in detail in FIG. 9 and, as shown therein, the upper end of thetension spring 174 is received in a peripheral groove 184 that extendsapproximately halfway around the wheel. The end of the spring is securedto a cross pin 185 within the adjacent one end of the groove. A stop pin188 extends radially through the wheel 180 and is secured for relativesliding movement in a radial direction by a screw 189 that intersectsthe radial aperture 190 in which the stop pin is located. The screw 189is received in a recess 191 of the stop pin, which recess is axiallyelongated to permit movement of the pin in the radial direction anamount equal to approximately the length of an end portion 188a ofsomewhat reduced diameter. The end portion 188a is receivable in one ofa plurality of peripherally spaced apertures 195 in the shaft 36. Byrotating the wheel about the shaft, and locating the end 188a of thestop pin 188 in a selected aperture 195, the tension on the spring onthe lower jaw member can be varied.

The incisal guide pin 62 carried by the maxillary plate 42 serves as ananterior stop for the lower jaw member to limit its upward movement. Theguide pin, as shown in FIG. 1 l, is an assembly that includes a stop pin198 with a threaded portion 198a that is threaded into a holder portion199. An integral collar 201 on the holder portion has two a lower flange202 and a central portion 204 with flat sides that cooperate with theslot 60 in the maxillary plate, to support and locate the pin. Athreaded end 206 of the holder portion 199 extends upwardly above thecollar 201 through the maxillary plate and receives a knurled clampingnut 208 that clamps the maxillary plate against the collar 201. Theupper end of the stop pin 198 extends above the threaded portion 206 andhas a knurled knob 209 that can be turned to extend the stop pin 198 orretract the stop pin relative to the holder portion 199. The holderportion 199 is split at its lower end as shown at 210 and tensionedinwardly to load the stop pin and eliminate any looseness or play. Withthis arrangement, the incisal guide pin assembly can be removed withoutchanging its setting relative to the maxillary plate and is rigid foruse of a cam follower on an incisal table that can be carried by thelower jaw member. By adjustment of the knob 209, the pin can be extendedto open the bite to compensate for the thickness of articulating papersand to change the freeway space between dental arch casts. The pin canalso be used to make jaw movement tracmgs.

Upper and lower dental arch casts DU and DL (FIG. and also in phantom inFIG. 1) illustrate the manner in which the casts are secured to thearticulator by upper and lower mounting plates 212, 213 and associatedsponge walls 214, 215 against which the dental arch casts arepositioned. The structure is shown in more detail in FIG. 13. Themounting plates and sponge walls are mirror images, and only the plate213 and wall 215 will be described in detail. The plate includes acentral threaded aperture 217 for receiving a threaded shaft portion ofthe knob 91 that is received within a slot 221 of the tongue 80, tosecure the mounting plate to the movable mandibular plate 78 withoutinterfering with the movement of the plate relative to the tongue. Twoadditional locating apertures 223, 224 are formed in the lower surfaceof the mounting plate 213 for receiving the locating pins 88, 89 of themandibular plate. The wall 215 is of cellular or sponge-like materialand is resilient. It extends about the periphery of the mounting plate213 and has a peripheral opening 229 at a location that faces forward oroutwardly of the articulator. The general shape of the mounting plate213 and peripheral wall 215 is compatible with the shape of the dentalarch.

Because of the resilience of the sponge-like cellular wall 215, thedental arch cast DL, adapted to rest against an edge 215a of the wall,conforms the wall to the contour of the opposed surface of the cast.Thus, the wall affords complete peripheral support and together with thecast and mounting plates form a cavity therebetween. The resilience ofthe two walls 214, 215 forces the two casts DU and DL against oneanother when the jaw plates 42, 78 are parallel, thereby holding the twocasts in a desired position, preparatory to affixing the costs to themounting plates with plaster. Plaster is introduced through the opening229 and into the cavity formed by the wall 215, the lower mounting plate213, and the lower dental cast DI... The plaster hardens while the lowereast is held by the resiliency of the wall in a desired positionrelative to the opposed cast and mounting plate. By virtue of theconstruction of the articulator and the location of the opening 229,plaster can be readily poured into the cavity formed by the wall 215when the articulator is supported utilizing the leg 30a of the L-shapedupright portion of the stand as a base.

OPERATION In use and by way of an initial summary, the articulatoradjustments are set to an initial condition to facilitate mounting upperand lower dental arch casts to a closed position determined with the aidof a bite registration and face bow. The casts are mounted and certainarticulator restraints are then removed. The jaw is then located in theexisting closed position, as dictated by the teeth. The condyle pivotassemblies of the articulator are used to determine the differencebetween the bite registration-determined and the existingtoothdetermined closed positions and a selection of a position is madeto which the reconstruction will be performed. Fossa slopes are then seton the articulator from measurements made on the patient with a face bowor protrusive bite registration. Relationships, principally of anteriorteeth, are determined with chewing movements, and posterior toothclearance is evaluated with lateral movements, facilitated by thearticulator.

Prior to mounting the dental arch casts, the following adjustments aremade to the articulator. The condyle pivot assemblies 68, 69 areadjusted so that the centering guide 164 is positioned within theaperture 170 of each lower jaw arm 64, 66 so that the ball element 130is centrally located, and the clamping nut 158 is tightened against thelowerjaw arms. The side shift adjustment screws 150, 151 are adjustedand tightened to lock the upper jaw element centrally of thearticulator. The mechanism -87 for moving it relative to the tongue 80,is set to a reference or zero position, as indicated by a scale (notshown) carried by the plate and tongue. The condyle ball elements arelocked in the retruded hinge position by the pins 146 and screws 147.Mounting plates 212, 213 are attached to the upper and lower plates 42and 78, and the jaw plates are locked in this mounting position bysecuring the latching lever 46 and the restraining linkage 94.

In mounting the casts with the aid of a bite registration and face bow,the determination of the closed (maximum intercuspal or centricocclusion) position of the cast is very important. The closed positiondetermines the relative heights and positions of the teeth and is thereference point from which movements are made. The closed position formost persons with good occlusion occurs with the condyles slightlyforward of their most retruded position. The retruded position orcentric relation of the condyles is the most repeatable position andtherefore used as a reference in determining the closed position of thecasts.

In mounting the casts in the articulator, a bite registration is used torelate the lower east to the upper cast, and a face bow is used tolocate the upper cast to the joint elements or pivot structures 38, 39of the articulator. The bite registration is made with rearward pressureon the chin of the patient so that the jaw is held in the retrudedposition. The dental arch casts are then placed in the indentations ofthe bite registration and supported between the sponges 214, 215 of themounting plates 212, 213. The face bow pointers, attached to the biteregistration, are then centered into the condyle pivot structures 68,69, a central aperture 130e at the outer end of the shaft 130b of theball 130 facilitating this. The face bow is centered between themounting plates 212,213, the articulator is placed on its back and ,1piztster slurry is poured into the openings 229 in the peripheral spongewalls. After the plaster has hardened, the bite registration and facebow are removed.

Adjustment of the mandibular plate 78 is achieved by rotating the screw85 to slide the plate 78 forward relative to the supporting tongue 80approximately onehalf millimeter, to correct for over retrusion of thejaw which occurred while making the bite registration. This adjustmentbrings the jaw directly forward and not down the fossae slopes. A spacebetween the casts, which exists with the removal of the biteregistration, is closed by releasing the anterior end of the lower linkpin 100, by loosening the screw 120, pivoting the lower jaw member aboutthe hinge axis until the casts are in tooth-to-tooth contact, and thenretightening the screw 120. The locking screws 147 for the condyle pinstops 146 need not be loosened for this hinge axis rotation. The castsare now located in the closed position determined by the biteregistration.

An existing or acquired (habitual) closed position for patients withenough opposing teeth can be found by placing the casts in their maximumintercuspal position. This position or any position can be achieved onthe articulator by loosening the nuts 158, the screw 120 that securesthe anterior end of the link pin 100, and the medial lateral positionscrews 150, 151. The centering guides 164 are withdrawn from theapertures 170 of the jaw arms 64, 66 and the tension springs 174, 176are released by the tension wheels 180, 182. This completely releasesthe lower jaw element from restraint within limited confines and thelower dental arch cast can be positioned into the upper cast, as theteeth dictate. With the lowerjaw thus in the existing closed position,the nuts 158, with the centering guides withdrawn are retightened sothat the front surface of the nut 158 clamps each arm 64, 66 against theflange 130d of the associated ball element 130, which is now somewhatoff center of the aperture 170. The screw 120 of the lower link pin 100is tightened, as are the adjustment screws 150, 151 to maintain theshaft 36 in the position dictated by the teeth. The difference betweenthe bite registration and existing closed positions is observable at theball elements 130 of the pivot assemblies 68, 69. If the biteregistration is made with the temporomandibular joints in their properpositions, then the difference between the existing and biteregistration positions, as indicated by the condyle assemblies, is themeasure of the harmony between the dentition and the temporomandibularjoints. The construction or reconstruction of the teeth can be built toeither the bite registration or the existing closed positions, or tosome intermediate compromise, without remounting the casts on the upperand lower plates of the articulator. If the ideal closed position ischosen, the nuts 158 are again loosened, the centering guides 164 aremoved inward into the apertures 170 to recenter the jaw element, and themedial lateral position adjustment screws 150, 151 are adjusted for jawcentrality.

The ability to release and reposition the lower cast and to indicate thechange in position at the condyles is also useful for comparing biteregistrations and, as a result, serves as an improved split casttechnique. For example, if several bite registrations are found toposition the casts in the same relationship, as measured at thecondyles, the retruded position was probably recorded by the biteregistrations, because protrusive jaw positions are seldom repeatable.

As the patients jaw is moved forward and back, the temporomandibularjoints allow the jaw condyles to translate along a narrow pathdetermined by the fossa of the temporal bone. In the profile view, thisfossa path is inclined with respect to the plane of the upper teeth. Theslope of this path may be different on each side and can be as shallowas 0 for some patients, and as great as 60 for others. Since theinclination of this path is so dependent on the particular patient andbecause it is very important in determining the clearance of theposterior teeth, an adjustment for the fossa inclination is provided oneach side of the articulator. Measuring the patients fossa paths iscommonly achieved with either a face bow or a protrusive biteregistration. In the first method, a face bow is attached to a biteregistration and the bite registration is cemented to the patients jawteeth. As the patients jaw is moved forward and back, face bow pointersnear the joints scribe lines on the skin or on a skull reference plate.The angle of the scribed lines is then measured with respect to theplane of the upper teeth and the angle of the surfaces 132c are setaccordingly by rotating the insert 133 of each pivot assembly 38, 39. Inthe second method, a protrusive bite registration is made and placedbetween the casts in the articulator. The surfaces 132c representing thefossa inclinations are then adjusted on the articulator so that thecasts seat properly in the protrusive bite registration.

In beginning the reconstruction a desired closed position is selectedbased on either the existing or the bite registration occlusion, and theteeth are built thereto. The lowerjaw element is locked in a fixedposition with the stop pins 146 and the restraining linkage 94, and theupperjaw element is opened and closed around the hinge axis provided bythe shaft 36, as the operator requires access to the work. Theadjustment provided by the adjustment screw and movable plate 78 of thelower jaw element and the medial-lateral position screws 150, 151 can bevaried to produce anteriorposterior and side-to-side freedom of movementin the closed position, if desired. By loosening the pin at the screw120, the lower jaw can be opened slightly around the hinge axis providedby the pivot structure 38, 39, and coincident with the axis of the shaft36, to compensate for the thickness of articulating papers that may beused.

With maximum intercuspal position established, the tension applied bythe springs 174, 176 is reapplied by rotating the tension wheels 180,182 and securing them in a position that tensions the springs, with thestop pins 188. The condyle ball pivot structures 130 are released bywithdrawing the pin stops 146. The upper jaw plate 42 should be lockedin a horizontal or lowered position by the latching lever 49 and latch46. The relationships of principally the anterior teeth are nowdetermined with chewing movements when the lower link 100 is securelyclamped at both ends to establish a fixed length, initially with theposterior end tightened in the most upward position in the slot 92. Theposterior end of the link is then incrementally moved downward, with theknob 106 being retightened each timev Because the arc of the curvedfinger 90 is not circular with a center at the universal joint 98, thescrew must be loosened for each shift in position of the posterior endof the link so that the closed position (maximum intercuspal position)remains the same.

At each position of the lower link 94, the lower jaw element is moved toeach side of the central position. This procedure generates a full rangeof chewing movements for evaluating the teeth in mastication. Theposterior knob 106 of the lower link is finally adjusted downward untilthe flattest desired angle of approach of the lower jaw teeth relativeto the upper (viewed frontally) is achieved. Although the lower jawelement is movable when the lower link 94 is released and adjusted, theinter-dentated casts maintain the jaw in the same, desired closedposition until the link is retightened.

Tooth gliding movements can be performed with the articulator byloosening the screw 120 at the lower end of the link 100 to eliminatethe link constraint. Tooth gliding movements are important forevaluating posterior tooth clearance in the natural dentition andposterior tooth balance in the denture occlusion, during lateral andprotrusive movements. The lower cast is articulated against the fixedupper case during the tooth gliding.

Although one specific construction has been shown and described indetail, modifications thereof are contemplated, which retain certain butnot all of the novel and advantageous features. For example, themovement of the pivots of the lower jaw member, analogous to thecondyles of the jaw along a cam surface to provide movement analogous tothat of the condyl along the fossa of the temporomandibular joint, canbe restrained with different structure than that shown, as by separatepivoted links secured at a lower end to the stand and which carry thecondyle pivots at the upper ends, and which ride along cam surfaces.Also, the lower restraint of the lower jaw movement can be achieved bytwo links rather than one. For example, one link can be provided on eachside of the lower jaw plate, secured at a forward location to the standthrough a universal joint, and the rearward or posterior end can beadjustably located in curved slots of the lower jaw mechanism to controlchewing motions and to adjust the angle of approach of the lower jaw tothe upper in articulation.

From the foregoing description it will be understood that an articulatorhas been provided that, in its concepts, utilizes a prime linkconstraint in combination with joint area constraints that include cams,a posterior stop, and condyle path grooves or condyle links. Variouscombinations of the prime link and joint con straints are utilized toduplicate such jaw positions and motions as (l) the cementing or biteregistration position, (2) any other bite registration position, (3) theexisting or acquired closed position, (4) a full range of chewingclosure motions, both toward left side and toward right side, (5) hingeaccess movement, (6) protrusive movement, and (7) tooth glidingmovements.

Modifications and alterations of the articulator described herein may bemade without departing from the spirit and scope of the inventiondefined in the appended claims.

What is claimed is:

l. A dental articulator comprising a support, two generally opposedjaw-like first and second connections between one said member and thesupport that permit complex movement of said one member relative to theother, and means, including a rigid link functionally constant in lengthbetween said one member and the support pivotally connected to both, toconstrain said movement of said one member relative to said support tosimulate chewing movement.

2. An articulator as set forth in claim 1 wherein said first and secondconnections comprise movable pivots. 3. An articulator as set forth inclaim 1 including means to change the location of at least one of saidlink connections to adjust its angular relationship with respect to saidsupport and said one member to change the range of movement of said onemember relative to said support.

4. A dental articulator comprising first and second structures, eachadapted to support a dental arch cast in opposing relationship to theother; means at two 10- cations of said first structure interengagedwith said second structure at two locations to allow said firststructure to move relative to said second structure with more than onedegree of freedom; and means, including a rigid link functionallyconstant in length connected for universal pivoting at two locations,one location fixed with respect to the first structure and the otherfixed with respect to the second structure, for providing one constraintfor the movement of said first structure relative to said secondstructure.

5. A dental articulator as set forth in claim 4 wherein said secondstructure includes a support, a plate for supporting a dental arch andmeans defining a fixed axis about which said plate is selectivelypivotable.

6. A dental articulator as set forth in claim 4 wherein said rigid linkis adjustable in length.

7. A dental articulator as set forth in claim '4 including means forchanging one of said two locations at which the link is connected. I

8. A dental articulator as set forth in claim 1 including means torelease said link at one of said locations to eliminate its restraint ofmovement of said first structure, and means to establish a fixed pivotaxis at said interengaged means between said first and secondstructures.

9. A dental articulator as set forth in claim 4 wherein said firststructure includes a first plate for supporting a dental arch cast andsaid second structure includes a stand and a second plate for supportinga dental arch cast, said second plate is located vertically above thefirst plate, and including means to secure said second plate in a fixedposition relative to the stand analogous to a maxilla, and meanssecuring said first plate to said first structure for articulationrelative to the stand in an analogous manner to a mandible.

10. A dental articulator comprising a stationary support and a movablejaw member, means, including two portions of said jaw memberinterconnected with said support, for providing relative movementbetween the support and jaw member with a plurality of degrees offreedom that permit lateral movement of the jaw member to the left andright of a central position relative to said support, and single rigidlink means functionally constant in length connected between a thirdportion of the jaw member that is displaced from an axis through saidtwo portions and a point on the support, to maintain said third portiona constant distance from said point on the support and to constrainmovement of said jaw member in directions both left and right of thecentral position.

11. A dental articulator comprising a support, a maxillary memberpivotably connected to said support and adapted to support a dental archcast, a manibular member movable relative to said support, saidmandibular member including a plate adapted to support a dental archcast and also including two means located to one side of a plane definedby said mandibular plate for interconnecting the mandibular member withsaid support for relative translational and pivotal movement, and arigid link on an opposite side of said plane from said two portions,connected between a third portion of said mandibular member and a pointon said support, a universal pivot at each connection of said link, andmeans permitting adjustment of at least one of the locations ofconnection for the link to increase or decrease an angular relationshipbetween the link and an imaginary plane defined by said point on thesupport and said two portions of the mandibular member.

12. A dental articulator as set forth in claim 11 wherein said meanspermitting adjustment of the location at which said link is connectedincludes a curved member providing different locations for connection ofsaid link on one of said jaw member and support.

13. A dental articulator as set forth in claim 11 including means tochange the length of the link between said two locations of connectionto pivot the mandibular member relative to said maxillary member andthereby change the distance between the plates thereof.

14. A dental articulator comprising a support, a maxillary plate carriedby said support, means hinging said maxillary plate to the support forrotational movement about a single axis, a mandibular plate, meansconnecting said mandibular plate to said support at two locations forrotational movement about plural axes, one of said plural axes beingcoincident with said single axis.

15. A dentalarticulator as set forth in claim 14 including means to lockthe maxillary plate in fixed relationship to the support.

16. A dental articulator as set forth in claim 14 including means torestrict pivoting of said mandibular plate to universal pivoting aboutonly one of said two locations.

17. A dental articulator as set forth in claim 14 including a rigid linkextending between said mandibular plate and said support and pivotallyconnected to both.

18. A dental articulator as set forth in claim 17 including adjustmentmeans connected with said link for changing the position of themandibular plate relative to the maxillary plate.

19. A dental articulator comprising a support stand, a first memberadapted to support a dental arch cast and carried by said stand, meanssecuring said first member to said stand for rotational movement about asingle fixed axis; a second member adapted to support a dental arch castin generally opposed relationship to said first member and carried bysaid stand, and means securing said second member to said stand forrotational movement about a plurality of axes, including an axiscoincident with said single fixed axis.

20. A dental articulator as set forth in claim 19 including a rigidlinking means pivotally connected to and extending between said secondmember and said stand for permitting movement of said second memberrelative to said stand when said second member pivots about axes notcoincident with said single fixed axis and which prevents movement ofsaid second member relative to said stand about an axis coincident withsaid single fixed axis, and means for releasing the connection betweensaid rigid linking means and one of said stand and second member.

21. A dental articulator comprising a stand, two supports for dentalarch casts carried by said stand, two pivots on one of said supportswith a common axis, two spaced pivot supports on said stand forreceiving said pivots, said pivot supports each providing an elongatedpath of restrictive movement for said pivots, means securing said pivotsupports to said stand for angular adjustment of said paths about acommon axis, and means on said stand providing a fixed pivot axis forthe other of said supports coincident with said last-mentioned commonaxis.

22. An articulator as set forth in claim 21 wherein said pivot supportsare each in the form of a guide with a groove that receives the end ofone of said pivots.

23. An articulator as set forth in claim 22 wherein each of said pivotsterminates in a spherical surface and each of said grooves has a backsurface that is inclined relative to a plane perpendicular to saidcommon axis of the guides.

24. An articulator as set forth in claim 22 wherein the common axis ofangular adjustment through said pivot guides is adjacent one end of eachof said grooves so that the center of said pivots coincides with thecommon axis when the pivots are at said one end of the grooves.

25. A dental articulator comprising a stand, two supports for dentalarch casts carried by said stand, two pivots on one of said supportswith a common axis, two spaced pivot supports each providing anelongated path of restrictive movement for said pivots and each in theform of a guide with a groove that receives an end of one of saidpivots, and means securing said pivot supports to said stand for angularadjustment of said paths about a common axis adjacent one end of each ofsaid grooves so that the center of said pivots coincides with the commonaxis when the pivots are at said one end of the grooves, each saidgroove having a back surface that converges toward that of the other ina direction along the length of the groove from said common axis ofadjustment.

26. A dental articulator comprising a support frame, two members withdental arch support portions in generally opposed relationship carriedby said frame, one having two pivot parts movable relative to the frameto provide translational and rotational movement of said one memberrelative to the frame, rigid link means functionally constant in lengthpivotally connected between the frame and said one member to constrainmovement of said one member relative to the frame, two cam surfaces oneadjacent each of said two pivot parts to control movement of said onemember in a direction along an axis defined by said pivot parts, andmeans carried by said frame for receiving said pivot parts and limitingmovement thereof to elongated paths.

27. A dental articulator comprising a support frame, two supportscarried by said frame representative of upper and lower jaws, one ofsaid supports having two oppositely projecting pivot members, twogrooves on said frame, each receiving one of said pivot members andconstraining the received members to movement along the grooves, two camsurfaces carried by said frame and converging toward one another forconstraining movement of each of said pivot members in its projectingdirection, and a single rigid link functionally constant in lengthpivotally connected to both said one support and said frame.

28. An articulator comprising a support, a member carried by saidsupport, cooperating connecting means on said member and the support attwo locations to permit articulation between the member and the support,means to selectively establish a fixed pivot axis location betweencooperating connecting means. and a position adjustment connectionbetween the member and the connecting means thereon to permitselectively changing the location of the connecting means on the member.

29. Apparatus as set forth in claim 28 wherein said position adjustmentconnection includes means to selectively reestablish one particularlocation between the member and the connecting means.

30. An articulator as set forth in claim 28 wherein said connectingmeans at each of said two locations is comprised of an elongated guideslot on said support and a ball connected to said member and engagedwith said guide slot and said means to selectively establish a fixedpivot axis includes means to prevent movement of said ball along saidslot while permitting rotational movement thereof.

31. In a dental articulator, structure for interconnecting a dental archsupport to a stand for relative translation and rotation, said structureincluding two spaced members on said support, two spaced receptacles onsaid stand located to concurrently receive said members for relativerotational and translational movement, and means to selectively changethe locations of said spaced members on the support to change therelationship of the support relative to the stand.

32. Apparatus as set forth in claim 31 including means to selectivelyestablish one particular location of each said spaced member relative tosaid support.

33. Apparatus as set forth in claim 32 wherein said means to selectivelyestablish one particular location of said spaced member relative to thesupport includes a clamping nut with a counterbore, a circular aperturein the support, an annular centering guide movable in an axial directionwithin the counterbore of the clamping nut such that when the annularcentering guide is extended axially beyond the clamping nut, its outsidediameter is closely received within the circular aperture in the supportand when the centering guide is retracted within the clamping nut, noeffective restraint exists between the centering guide and the support.

34. Apparatus as connected forth in claim 33 wherein said centeringguide is connencted by pins, which project through axial slots in theclamping nut, to a sleeve surrounding the clamping nut, such thatrotation of the sleeve produces rotation of the clamping nut andcentering guide, and sliding movement of the sleeve produces a slidingmovement of the centering guide relative to the nut.

35. Apparatus as set forth in claim 32 wherein said means to selectivelyestablish one particular location of said spaced member relative to saidsupport includes a knob with a threaded bore, one end of the knob beingflat and perpendicular to the axis of the threaded bore for clamping themember in a range of positions relative to the support, and with theother end shaped for positive seating of the member at one particularlocation relative to the support.

36. Apparatus as set forth in claim 31 wherein each said spaced memberincludes a pin offset from the central axis of the spaced member, whichis received by an elongated slot in the said support such thatrotational movement of the spaced member relative to the support islimited.

37. Apparatus as set forth in claim 31 wherein said support has twoarms, said two spaced members are each adjustably secured to a differentone of said anns, and each receptacle includes an elongated aperturethat receives and guides movement of one of said spaced members.

38. Apparatus as set forth in claim 37 wherein said spaced members areball pivots, and said apertures are located with one portion of eachdefining a pivot axis for rotational movement of said support relativeto said stand, each aperture extending from said axis in a generallycommon direction with the other aperture, and said structure furtherincluding means to retain said ball pivots at said pivot axis.

39. Apparatus as set forth in claim 38 wherein said receptacles aremovable relative to said stand to change the direction at which saidapertures extend from the axis.

40. A dental articulator comprising a stand, two supports for dentalcasts carried by said stand in generally opposed relationship, meansconnecting at least one of said supports to the stand for relativepivotal movement, a stop member extending between said two supports tolimit the proximity of the supports to one another, said stop memberincluding means to adjust the effective length of the stop memberbetween the two supports, means to releasably secure the stop members toone of said supports for removal without changing the effective length,two concentric relatively movable parts one of which is pin-like andmovable longitudinally relatively to the other, and spring pretensionmeans yieldably retaining said movable parts in longitudinally adjustedpositions.

41. A dental articulator comprising a stand having a primary baseportion and a frame portion extending therefrom, said frame portionforming a secondary base portion with said primary base portion orientedat approximately to the primary base portion, two dental arch castsupport elements secured to said frame portion in generally opposedrelationship, at least one of which is pivotally secured to said frameportion, said elements being positionable horizontally when said standis supported with its primary base portion horizontal and verticallywhen said stand is supported with its secondary base portion horizontal,a receptacle secured to each of said support elements in opposedrelationship for use in securing dental arch casts to said elements,said receptacles each including a side portion extending in a directionfrom the associated support element toward the other and forming aperipheral receiving surface for a dental arch cast, and an opening inthe side portion located to face upward when said secondary base portionis horizontal.

42. A dental articulator as set forth in claim 41 wherein said sideportion is deformable.

43. A dental articulator as set forth in claim 42 wherein said sideportion is resilient.

44. A dental articulator as set forth in claim 41 wherein said sideportion is a foamed sponge-like resilient material.

45. A device for securing a dental arch cast to a support member of anarticulator, comprising a base and a readily deformable wall secured tosaid base, extending therefrom along a path defining a concave shape andwith a distal surface adapted to receive a dental arch cast.

46. A device as set forth in claim 45 wherein said wall is resilient.

47. A device for yieldably supporting a dental arch cast andconstraining a hardenable material in contact with the arch cast,comprising a compressibly yieldable and resilient barrier means capableof temporarily supporting a dental arch cast and retaining a flowablehardenable material, shaped to form a receptacle for flowable hardenablematerial and having an opening in the barrier means through which saidmaterial can be introduced.

48. A device as set forth in claim 47 wherein said barrier means isformed of sponge-like material.

49. ln combination, a dental articulator with two dental arch supportmembers in generally opposed relatively pivotable, relationship andsoft, resilient, positioning members carried by said support members forsupporting and resiliently urging dental arches into opposedinterengagement during mounting.

S0. A dental articulator comprising a base, two supports carried by saidbase, each adapted to support a dental arch cast, means securing one ofsaid supports to the base for relative pivotal movement, a plate carriedby one of said supports, means securing the plate to the carryingsupport for relative movement in the plane of said plate, guide means tolimit the movement in said plane to a straight path in a directionperpendicular to a plane containing the pivot axis of said pivotallysecured support, positive drive means to provide controlled movement ofsaid plate along said path, and a spring bias acting perpendicularly toand between said plate and carrying support to yieldably maintainposition of said plate relative to said support.

51. An articulator comprising a support, a member carried by saidsupport, cooperative connecting means on said member and the support attwo locations to permit articulation between the member and the support,and adjustable biasing means to urge the member and support in thedirection of articulated movement, said adjustable biasing meansincluding a tension wheel rotatably supported on a shaft of the support,a tension spring secured between the tension wheel and the member, and astop pin extending radially through the wheel and movable to selectivelyengage in one of a number of apertures in the shaft to control therotational position of the wheel and hence the tension of the spring.

52. An articulator comprising a support, a member carried by saidsupport, a shaft on the support movable axially, cooperative connectivemeans on said member and the support carried at two locations on theshaft and constructed to permit articulation between the member and thesupport, and means to laterally shift the shaft relative to the support,including two screws movable in threaded bores, of the support inclinedtoward one another and acting on and substantially perpendicularly togenerally opposed surfaces on said shaft.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3908271 DATED September 30, 1975 INVENTOMS): Harry J. Derdaand Charles H. Gibbs fimcmmmdmmamrwmmsmmewWeJMMWwpMWtmdmmsmdLflmwPmwtamhwdwcmmdwasdmwnmmw Column 3, line 2, "aactual" should be actual Column4, line 45, after "is" confined was omitted;

line 45, erase "t";

Column 9, line 54, "connecting" should be connection Column 11, line 1,cancel "two".

In the C laims:

Claim 8 (Column 16, line 33) change "1" to 4 Signed and Scalcd thissixteenth D ay Of December 1 9 75 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer 7 Commissioneroflarents and Trademarks

1. A dental articulator comprising a support, two generally opposedjaw-like first and second connections between one said member and thesupport that permit complex movement of said one member relative to theother, and means, including a rigid link functionally constant in lengthbetween said one member and the support pivotally connected to both, toconstrain said movement of said one member relative to said support tosimulate chewing movement.
 2. An articulator as set forth in claim 1wherein said first and second connections comprise movable pivots.
 3. Anarticulator as set forth in claim 1 including means to change thelocation of at least one of said link connections to adjust its angularrelationship with respect to said support and said one member to changethe range of movement of said one member relative to said support.
 4. Adental articulator comprising first and second structures, each adaptedto support a dental arch cast in opposing relationship to the other;means at two locations of said first structure interengaged with saidsecond structure at two locations to allow said first structure to moverelative to said second structure with more than one degree of freedom;and means, including a rigid link functionally constant in lengthconnected for universal pivoting at two locations, one location fixedwith respect to the first structure and the other fixed with respect tothe second structure, for providing one constraint for the movement ofsaid first structure relative to said second structure.
 5. A dentalarticulator as set forth in claim 4 wherein said second structureincludes a support, a plate for supporting a dental arch and meansdefining a fixed axis about which said plate is selectively pivotable.6. A dental articulator as set forth in claim 4 wherein said rigid linkis adjustable in length.
 7. A dental articulator as set forth in claim 4including means for changing one of said two locations at which the linkis connected.
 8. A dental articulator as set forth in claim 1 includingmeans to release said link at one of said locations to eliminate itsrestraint of movement of said first structure, and means to establish afixed pivot axis at said interengaged means between said first andsecond structures.
 9. A dental articulator as set forth in claim 4wherein said first structure includes a first plate for supporting adental arch cast and said second structure includes a stand and a secondplate for supporting a dental arch cast, said second plate is locatedvertically above the first plate, and including means to secure saidsecond plate in a fixed position relative to the stand analogous to amaxilla, and means securing said first plate to said first structure forarticulation relative to the stand in an analogous manner to a mandible.10. A dental articulator comprising a stationary support and a movablejaw member, means, including two portions of said jaw memberinterconnected with said support, for providing relative movementbetween the support and jaw member with a plurality of degrees offreedom that permit lateral movement of the jaw member to the left andright of a central position relative to said support, and single rigidlink means functionally constant in length connected between a thirdportion of the jaw member that is displaced from an axis through saidtwo portions and a point on the support, to maintain said third portiona constant distance from said point on the support and to constrainmovement of said jaw member in directions both left and right of thecentral position.
 11. A dental articulator comprising a support, amaxillary member pivotably connected to said support and adapted tosupport a dental arch cast, a manibular member movable relative to saidsupport, said mandibular member including a plate adapted to support adental arch cast and also including two means located to one side of aplane defined by said mandibular plate for interconnecting themandibular member with said support for relative translational andpivotal movement, and a rigid link on an opposite side of said planefrom said two portions, connected between a third portion of saidmandibular member and a point on said support, a universal pivot at eachconnection of said link, and means permitting adjustment of at least oneof the locations of connection for the link to increase or decrease anangular relationship between the link and an imaginary plane defined bysaid point on the support and said two portions of the mandibularmember.
 12. A dental articulator as set forth in claim 11 wherein saidmeans permitting adjustment of the location at which said link isconnected includes a curved member providing different locations forconnection of said link on one of said jaw member and support.
 13. Adental articulator as set forth in claim 11 including means to changethe length of the link between said two locations of connection to pivotthe mandibular member relative to said maxillary member and therebychange the distance between the plates thereof.
 14. A dental articulatorcomprising a support, a maxillary plate carried by said support, meanshinging said maxillary plate to the support for rotational movementabout a single axis, a mandibular plate, means connecting saidmandibular plate to said suppOrt at two locations for rotationalmovement about plural axes, one of said plural axes being coincidentwith said single axis.
 15. A dental articulator as set forth in claim 14including means to lock the maxillary plate in fixed relationship to thesupport.
 16. A dental articulator as set forth in claim 14 includingmeans to restrict pivoting of said mandibular plate to universalpivoting about only one of said two locations.
 17. A dental articulatoras set forth in claim 14 including a rigid link extending between saidmandibular plate and said support and pivotally connected to both.
 18. Adental articulator as set forth in claim 17 including adjustment meansconnected with said link for changing the position of the mandibularplate relative to the maxillary plate.
 19. A dental articulatorcomprising a support stand, a first member adapted to support a dentalarch cast and carried by said stand, means securing said first member tosaid stand for rotational movement about a single fixed axis; a secondmember adapted to support a dental arch cast in generally opposedrelationship to said first member and carried by said stand, and meanssecuring said second member to said stand for rotational movement abouta plurality of axes, including an axis coincident with said single fixedaxis.
 20. A dental articulator as set forth in claim 19 including arigid linking means pivotally connected to and extending between saidsecond member and said stand for permitting movement of said secondmember relative to said stand when said second member pivots about axesnot coincident with said single fixed axis and which prevents movementof said second member relative to said stand about an axis coincidentwith said single fixed axis, and means for releasing the connectionbetween said rigid linking means and one of said stand and secondmember.
 21. A dental articulator comprising a stand, two supports fordental arch casts carried by said stand, two pivots on one of saidsupports with a common axis, two spaced pivot supports on said stand forreceiving said pivots, said pivot supports each providing an elongatedpath of restrictive movement for said pivots, means securing said pivotsupports to said stand for angular adjustment of said paths about acommon axis, and means on said stand providing a fixed pivot axis forthe other of said supports coincident with said last-mentioned commonaxis.
 22. An articulator as set forth in claim 21 wherein said pivotsupports are each in the form of a guide with a groove that receives theend of one of said pivots.
 23. An articulator as set forth in claim 22wherein each of said pivots terminates in a spherical surface and eachof said grooves has a back surface that is inclined relative to a planeperpendicular to said common axis of the guides.
 24. An articulator asset forth in claim 22 wherein the common axis of angular adjustmentthrough said pivot guides is adjacent one end of each of said grooves sothat the center of said pivots coincides with the common axis when thepivots are at said one end of the grooves.
 25. A dental articulatorcomprising a stand, two supports for dental arch casts carried by saidstand, two pivots on one of said supports with a common axis, two spacedpivot supports each providing an elongated path of restrictive movementfor said pivots and each in the form of a guide with a groove thatreceives an end of one of said pivots, and means securing said pivotsupports to said stand for angular adjustment of said paths about acommon axis adjacent one end of each of said grooves so that the centerof said pivots coincides with the common axis when the pivots are atsaid one end of the grooves, each said groove having a back surface thatconverges toward that of the other in a direction along the length ofthe groove from said common axis of adjustment.
 26. A dental articulatorcomprising a support frame, two members with dental arch supportportions in gEnerally opposed relationship carried by said frame, onehaving two pivot parts movable relative to the frame to providetranslational and rotational movement of said one member relative to theframe, rigid link means functionally constant in length pivotallyconnected between the frame and said one member to constrain movement ofsaid one member relative to the frame, two cam surfaces one adjacenteach of said two pivot parts to control movement of said one member in adirection along an axis defined by said pivot parts, and means carriedby said frame for receiving said pivot parts and limiting movementthereof to elongated paths.
 27. A dental articulator comprising asupport frame, two supports carried by said frame representative ofupper and lower jaws, one of said supports having two oppositelyprojecting pivot members, two grooves on said frame, each receiving oneof said pivot members and constraining the received members to movementalong the grooves, two cam surfaces carried by said frame and convergingtoward one another for constraining movement of each of said pivotmembers in its projecting direction, and a single rigid linkfunctionally constant in length pivotally connected to both said onesupport and said frame.
 28. An articulator comprising a support, amember carried by said support, cooperating connecting means on saidmember and the support at two locations to permit articulation betweenthe member and the support, means to selectively establish a fixed pivotaxis location between cooperating connecting means, and a positionadjustment connection between the member and the connecting meansthereon to permit selectively changing the location of the connectingmeans on the member.
 29. Apparatus as set forth in claim 28 wherein saidposition adjustment connection includes means to selectively reestablishone particular location between the member and the connecting means. 30.An articulator as set forth in claim 28 wherein said connecting means ateach of said two locations is comprised of an elongated guide slot onsaid support and a ball connected to said member and engaged with saidguide slot and said means to selectively establish a fixed pivot axisincludes means to prevent movement of said ball along said slot whilepermitting rotational movement thereof.
 31. In a dental articulator,structure for interconnecting a dental arch support to a stand forrelative translation and rotation, said structure including two spacedmembers on said support, two spaced receptacles on said stand located toconcurrently receive said members for relative rotational andtranslational movement, and means to selectively change the locations ofsaid spaced members on the support to change the relationship of thesupport relative to the stand.
 32. Apparatus as set forth in claim 31including means to selectively establish one particular location of eachsaid spaced member relative to said support.
 33. Apparatus as set forthin claim 32 wherein said means to selectively establish one particularlocation of said spaced member relative to the support includes aclamping nut with a counterbore, a circular aperture in the support, anannular centering guide movable in an axial direction within thecounterbore of the clamping nut such that when the annular centeringguide is extended axially beyond the clamping nut, its outside diameteris closely received within the circular aperture in the support and whenthe centering guide is retracted within the clamping nut, no effectiverestraint exists between the centering guide and the support. 34.Apparatus as connected forth in claim 33 wherein said centering guide isconnencted by pins, which project through axial slots in the clampingnut, to a sleeve surrounding the clamping nut, such that rotation of thesleeve produces rotation of the clamping nut and centering guide, andsliding movement of the sleeve produces a sliding movement of thecentering guide relative to the nut.
 35. Apparatus as set forth in claim32 wherein said means to selectively establish one particular locationof said spaced member relative to said support includes a knob with athreaded bore, one end of the knob being flat and perpendicular to theaxis of the threaded bore for clamping the member in a range ofpositions relative to the support, and with the other end shaped forpositive seating of the member at one particular location relative tothe support.
 36. Apparatus as set forth in claim 31 wherein each saidspaced member includes a pin offset from the central axis of the spacedmember, which is received by an elongated slot in the said support suchthat rotational movement of the spaced member relative to the support islimited.
 37. Apparatus as set forth in claim 31 wherein said support hastwo arms, said two spaced members are each adjustably secured to adifferent one of said arms, and each receptacle includes an elongatedaperture that receives and guides movement of one of said spacedmembers.
 38. Apparatus as set forth in claim 37 wherein said spacedmembers are ball pivots, and said apertures are located with one portionof each defining a pivot axis for rotational movement of said supportrelative to said stand, each aperture extending from said axis in agenerally common direction with the other aperture, and said structurefurther including means to retain said ball pivots at said pivot axis.39. Apparatus as set forth in claim 38 wherein said receptacles aremovable relative to said stand to change the direction at which saidapertures extend from the axis.
 40. A dental articulator comprising astand, two supports for dental casts carried by said stand in generallyopposed relationship, means connecting at least one of said supports tothe stand for relative pivotal movement, a stop member extending betweensaid two supports to limit the proximity of the supports to one another,said stop member including means to adjust the effective length of thestop member between the two supports, means to releasably secure thestop members to one of said supports for removal without changing theeffective length, two concentric relatively movable parts one of whichis pin-like and movable longitudinally relatively to the other, andspring pretension means yieldably retaining said movable parts inlongitudinally adjusted positions.
 41. A dental articulator comprising astand having a primary base portion and a frame portion extendingtherefrom, said frame portion forming a secondary base portion with saidprimary base portion oriented at approximately 90* to the primary baseportion, two dental arch cast support elements secured to said frameportion in generally opposed relationship, at least one of which ispivotally secured to said frame portion, said elements beingpositionable horizontally when said stand is supported with its primarybase portion horizontal and vertically when said stand is supported withits secondary base portion horizontal, a receptacle secured to each ofsaid support elements in opposed relationship for use in securing dentalarch casts to said elements, said receptacles each including a sideportion extending in a direction from the associated support elementtoward the other and forming a peripheral receiving surface for a dentalarch cast, and an opening in the side portion located to face upwardwhen said secondary base portion is horizontal.
 42. A dental articulatoras set forth in claim 41 wherein said side portion is deformable.
 43. Adental articulator as set forth in claim 42 wherein said side portion isresilient.
 44. A dental articulator as set forth in claim 41 whereinsaid side portion is a foamed sponge-like resilient material.
 45. Adevice for securing a dental arch cast to a support member of anarticulator, comprising a base and a readily deformable wall secured tosaid base, extending therefrom along a path defining a concave shape andwith a distal surface adapted to receive a dental arch cast.
 46. Adevice as set forth in claim 45 wherein said wall is resilient.
 47. Adevice for yieldably supporting a dental arch cast and constraining ahardenable material in contact with the arch cast, comprising acompressibly yieldable and resilient barrier means capable oftemporarily supporting a dental arch cast and retaining a flowablehardenable material, shaped to form a receptacle for flowable hardenablematerial and having an opening in the barrier means through which saidmaterial can be introduced.
 48. A device as set forth in claim 47wherein said barrier means is formed of sponge-like material.
 49. Incombination, a dental articulator with two dental arch support membersin generally opposed relatively pivotable, relationship and soft,resilient, positioning members carried by said support members forsupporting and resiliently urging dental arches into opposedinterengagement during mounting.
 50. A dental articulator comprising abase, two supports carried by said base, each adapted to support adental arch cast, means securing one of said supports to the base forrelative pivotal movement, a plate carried by one of said supports,means securing the plate to the carrying support for relative movementin the plane of said plate, guide means to limit the movement in saidplane to a straight path in a direction perpendicular to a planecontaining the pivot axis of said pivotally secured support, positivedrive means to provide controlled movement of said plate along saidpath, and a spring bias acting perpendicularly to and between said plateand carrying support to yieldably maintain position of said platerelative to said support.
 51. An articulator comprising a support, amember carried by said support, cooperative connecting means on saidmember and the support at two locations to permit articulation betweenthe member and the support, and adjustable biasing means to urge themember and support in the direction of articulated movement, saidadjustable biasing means including a tension wheel rotatably supportedon a shaft of the support, a tension spring secured between the tensionwheel and the member, and a stop pin extending radially through thewheel and movable to selectively engage in one of a number of aperturesin the shaft to control the rotational position of the wheel and hencethe tension of the spring.
 52. An articulator comprising a support, amember carried by said support, a shaft on the support movable axially,cooperative connective means on said member and the support carried attwo locations on the shaft and constructed to permit articulationbetween the member and the support, and means to laterally shift theshaft relative to the support, including two screws movable in threadedbores, of the support inclined toward one another and acting on andsubstantially perpendicularly to generally opposed surfaces on saidshaft.